With only 296 members it is amazing how many of them share the same birthday

cheers

Andy

if images are not visible on my posts it is because Photobucket withdrew their free hosting service. I will reload images to the most recent threads in due course. Please drop me a PM if you would like to see anything before then

Pinch wrote:I used to study astrology and the Tarot - many moons ago when I was going through my hippy spiritual Goth years!

Andy, which zodiac star sign is the most popular amongst the members?

Sorry Paul, that would take me too long to work out. There are plenty of hairies around here though And probably one or two saggy teary * too

cheers

Andy

if images are not visible on my posts it is because Photobucket withdrew their free hosting service. I will reload images to the most recent threads in due course. Please drop me a PM if you would like to see anything before then

I've read and tried to understand that fact Gill. It appears that with a group of 23 there is a 50% change of two people having the same birthday. No matter how hard I try or how many times I have read the explanation I can still not get my head around that. But then ignorance is bliss

cheers

Andy

if images are not visible on my posts it is because Photobucket withdrew their free hosting service. I will reload images to the most recent threads in due course. Please drop me a PM if you would like to see anything before then

The way I see it, if "x" has a given birthday, then there is a 1 in 365 chance that "y" will have the same. Is it not then 2 in 365 or 1 in 182.5 for a 50% chance of having the same ? Or is that too simple ?

Last edited by chataigner on 10 Jan 2016, 15:08, edited 1 time in total.

chataigner wrote:The way I see it, if "x" has a given birthday, then there is a 1 in 365 chance that "y" will have the same. Is it not then 2 in 365 or 1 in 182.5 for a 50% chance of having the same ? Or is that too simple ?

I've just read the explanation, clearly it is too simple ! 1 in 365 (ish) is of course correct for 100% probability of two people having the same birthday, but a 50% probability does not equate to half a 100% probability.

It's taken a few minutes, but I think I've understood it and can express it in words. You start by comparing two people - so far easy, when you add a third, you are not comparing the third only with the first, but also with the second. When you add a fourth, he is compared with each of the 3 others and so on.

if images are not visible on my posts it is because Photobucket withdrew their free hosting service. I will reload images to the most recent threads in due course. Please drop me a PM if you would like to see anything before then

You are perhaps thinking the question is: of the other 22 people in the room, what is the chance one of them will share MY birthday. The actual question is what is the chance that ANY two people will share the same birthday. Because you are taking all pair-wise comparisons, you are actually comparing 253 possibilities.

Although you can use simple probability to calculate this, the data is also slightly skewed by not every day having an equal chance of people being born on it - think of the boom in babies in September for example (Christmas is 9 months before) or the smaller boom in April/May (if it was a hot summer the year before).

Statistics can be wonderful and bloody useless at the same time. Did you know the mean number of legs a human has is less than 2? This is because some people have one leg or no legs, but nobody has 3 legs!